100% reliable parachute deployment

[Frank]

Hello all,

Here are some pictures of the construction details of this parachute deployment system. It has many advantages. No batteries or computer, yet the timing of the deployment is completely controllable. It is cheap, and easy to make (made mine in 1 night). And, as the video shows, works like a charm to push the nosecone off and deploy the parachute. The construction photo details the assembly of a non-flying (but fully functional) mock up to give you the principles of the idea.

The cleverness is really in the "change of state" of all water rockets...loss of high pressure to atmospheric...so it is applicable to all water rockets. I can think of about five ways to employ this "bladder bearing" to release not only spring-loaded deployment systems, but even rubber-band ones! Most are even simpler than the one depicted, but this is what I wanted for my rocket. Here are the construction pix. I'm pretty sure only minimal commentary is necessary - but I welcome questions. Yes...it uses a plain old (medium thick walled) balloon available anywhere in the world.

The delay in deployment is controlled by the rate at which air leaves the balloon through the drilled-out spray bottle nozzle, as shown.

Here is the YouTube Video of the device in actual operation. The bladder-bearing can hold back HUGE amounts of spring tension! Feel free to use longer and/or stronger springs as suits your needs. To keep the video short, I started with the pressure had already been applied to the rocket. The nosecone and parachute are omitted so you can see the device in operation.

Best regards to all,

Frank

[youtube][/youtube]

[U.S. Water Rockets1]

Looks like a pretty good idea. Good thinking and good workmanship too.

[air.command]

Hi Frank,

Very nice work. How are you keeping the springs compressed while packing the parachute and before you pressurize the rocket? The video shows the operation very well. What pressure did you run the test at? What kind of timing range do you get by changing the hole in the spray nozzle? And one more question, how easy is to change the timing in the field if you change say the launch pressure or the amount of water in the rocket and you need to compensate for those changes?

Apologies for all the questions, I'm just curious about the design.

- George

[Frank]

Hi Frank,

Very nice work. How are you keeping the springs compressed while packing the parachute and before you pressurize the rocket? The video shows the operation very well. What pressure did you run the test at? What kind of timing range do you get by changing the hole in the spray nozzle? And one more question, how easy is to change the timing in the field if you change say the launch pressure or the amount of water in the rocket and you need to compensate for those changes?

Apologies for all the questions, I'm just curious about the design.

- George

Hi, George:
Please don't apologize for the questions. I've left out a lot of specific info largely because if someone wants to implement the general concept and design, they might want to make changes specific to their needs. The springs can be compressed and held pre-launch by a thin skewer stick passed thru the Correx and fuselage. It takes only the tiniest pressure (can easily do it with my own breath on the rocket nozzle) to put a tremendous grip on the three dowels. I was absolutely floored by how much tension this simple bladder-bearing can hold back.

The YouTube video posted was only run at 50 P.S.I. since I have no knowledge of the burst pressure of the Boullion cube bottle that I swiped from my wife to make this mock-up. A MUCH better choice (if you are going to stick with PET) is a tri-lobed Nyquil bottle. Excellent geometry for three springs - and will likely have a burst pressure far in excess of a soda bottle since they are so thick-walled. The fact that I limited the test to 50 PSI for safety does not invalidate anything, since it simply represents that portion of the flight where the pressures have dropped to that point.

So far, I've only tested the spray bottle nozzle limited in two ways...as provided by the manufacturer (WAY too slow) and drilled out with a 5/64" hole (as depicted in the photo) which gave me about a 3 second delay. I can envision an "infinitely variable" version made with a completely blocked threaded tube which is slotted at the easily accessible end. A sleeve which screws over the slotted threads could change the area of the slot through which air could escape so that the time to deployment could be dialed in on a bench or in the field to a fraction of a second with the simple twist of the wrist!

To tell the truth, I expect a major overhaul of this concept to make it far lighter, smaller, simpler, safer, and WAY stronger. Hint: It will use a short section of capped PVC (maybe 2"- 3" tall) drilled HORIZONTALLY at the very top. A short section of BICYCLE tire will be the bladder. Two turned pieces of wood (cut of sections of a hardwood dowel with a "waist" to allow the tire to be secured) just smaller than the ID of the PVC tube will enclose the end of the tire material and be the "bearing plate" at one end, and the means to introduce air at the other. If you prefer a spring device, a spring-loaded, very short piece of skewer sick can be passed thru the cap horizontally and act like a "pull-pin" to release whatever mechanism deploys the chute. In the alternative, a rubber-band can be directly passed thru the holes (use and keep attached to it a short piece of string to re-arm in seconds) and in each instance, when the pressure drops, the "pin" is pulled or the rubber band is release from the crush of the wood bearing block and viola, parachute deployment.

So...don't anyone fret over the current implementation, materials, and degree of difficulty in construction. Far simpler, smaller, and more robust versions are on the way which will leave much more room for a chute and other requisite payload!

Again, best to all.

Frank S.

[Frank]

OK...so the R & D on this concept has been inching forward with lots of failures and plenty of success to report as well. As recited above, I have continued to refine the materials to employ in implementing this "bladder bearing" chute deployment system, and have settled on bicycle tire inner tube as the bladder, and have tested a variety of "shell" materials. Some are more labor intensive to make but extremely light (rolled section of PET bottle glued with PL Premium) and some are heavy but takes only an hour to make (taped PVC clam shell as depicted here).

Both have demonstrated perfect performance to 90 PSI...I would expect both to hold to ~ 150 PSI, but have not tested to that pressure to date. Will do so when I return from my vacation in Costa Rica. I present a pix of the PVC shell and video of a bench test "deployment" at the end of a 90 PSI test flight. See: [youtube][/youtube]

By the way...there is NO restriction on the outlet of the bladder, so this represents the fastest it can deploy. Seems to be co-incident with the air-burst, so SOME restriction in indicated to allow time for the coast phase of the ascent. A work in progress, WITH some progress to report!

Best to all. See you in 2 weeks!

Frank

[U.S. Water Rockets1]

This concept could possibly be reduced in size to the point it could fit into a T-8 FTC. You could use a long thin balloon or some long thin latex bladder with an opening at one end sort of like a finger cut off a latex glove. You could put it inside a plastic cigar tube instead of a bottle or jar. It would have the same concept only in much smaller and lighter configuration.

[Frank]

Yes, it can be much further reduced in size and weight without impairing function because of the overwhelming side-forces, even in the much smaller implementation. That's why I'm so excited about this idea and have been pursuing it and reporting on it.

As a practical matter, I can tell you I hit many rough patches using bladders as thin as from latex gloves, thin walled balloons (marketed as animal twist balloons) and even medium-thick walled balloons (marketed as water balloons). They are flexible enough to herniate through ANY (and I mean ANY) space or hole that you give them. They inevitably encounter a sharp edge (and I've tried packing them off with cotton and making clever "trap doors" to cover the necessary holes) all to no avail. Result? BANG!!!!

So far, the bicycle inner tube has proved to be more than strong enough. Capped at both ends, it expands only in the middle section (looks like a fat Saturn with rings) and so long as the holes for the entry/exit of the actuating mechanism are kept to ONLY the top and bottom of the restraining container, no worries at all, and no doubt pressures can be raised to very water-rocket practical levels of 150 PSI - or even above!

The lightest (and most fun to make) are the PET tubes made from the mid-sections of soda bottles. I rolled them and glued them with PL Premium using PVC forms of the desired size and "clamped" them using tightly wound string during glue curing. OBVIOUSLY light as a feather and strong enough for the application as they end up in 2 1/2 wraps in the smaller sizes, and can be built up with the material from two bottles if a modest size tube is required. You can make 5 or 6 in one sitting this way!

I'm still in the "proof of concept" and "safety at pressure" stage of this deployment system, but have VERY high hopes it will be useful to all water rocket enthusiasts as an extremely reliable way to predictably deploy a parachute at apogee, and no other time. My wife is very proud of me for having thought this up, and I know of no other person who has ever implemented such a thing before, so it represents my first solo water rocketry contribution. She's actually helped me out by donating containers from her kitchen!

There are so many advantages to using this system of deployment. Simple. Cheap. Small and lightweight (eventually). No early deployment. No heavy batteries. No complicated or expensive electronics to lose or have destroyed (RC receivers, computers). Great anchor point (at the coupling) for the parachute. Easy bench testing to dial in the timing of deployment. Absolutely reliable, repeatable deployment timing.

OK...gotta go! Hope to find many comments and/or questions and/or constructive criticisms when I get back from Costa Rica in 2 weeks. Been married 25 years and this is our anniversary trip, so I have to put all this aside for 14 days.

Best to all,

Frank S.

[Frank]

OK...had time to photo this smaller, much lighter version. Have full expectations I will fly this one! Weighs next to nothing. No issues w/r/t strength of containment of this aluminum can.

Best,

Frank

[Frank]

OK..Hi, all!

Back from Costa Rica...gorgeous! Pura Vida!!! Anyhow...here's the BEST implementation yet of my post-thrust pressure released parachute deployment system. Sturdy, cheap, easy, lightweight and 100% successful in multiple bench tests. Can be made half the size depicted with ease, still with incredible gripping power, meaning the power employed in ejection can be quite powerful (if necessary) also. Since a picture is worth 1000 words, here are 2 pictures and one video. This implementation I consider 100% flyable. The difference between THIS version and all the prior ones is that there is an INTERNAL 1/2" PVC tube with holes drilled in it (four) to inflate the skinniest bicycle tire I could find. This internal tube made sealing the tire a snap! A 1" I.D. tube forms the outer bearing wall. A short section of rubber band provides the ejecting power.

I've tested it to 100 p.s.i. multiple times and it didn't turn a hair. Worked EVERY time! Here's an uploaded YouTube video at 100 p.s.i.


PLEASE...somebody else build this and let me know how it works out for you!!!!

Best to all!

Frank

[U.S. Water Rockets1]

OK...had time to photo this smaller, much lighter version. Have full expectations I will fly this one! Weighs next to nothing. No issues w/r/t strength of containment of this aluminum can.

Best,

Frank

Is that still made using a bike inner tube? The diameter of the rubber tube looks very thin, almost too thin to be a bike inner tube.

[Frank]

Yes...it's a bike inner tube. Here's a picture of the box with all the info. Salvaged the box from my work shop garbage can. Says the wall thickness is .9mm.

Best,

Frank S.

[RebelRockets]

Hi Frank,

Congratulations on your success with the device!

Last summer I bought some latex rubber hose to try to make a "crushing sleeve" type of staging device but never got very far into that idea. It is 1/4 inch i.d., 3/8 o.d., and was sold by the foot at Lowe's and I think it is available in long lengths at Home Depot. After seeing your idea here, I started thinking about using latex hose in your type of device.

When very low pressure is applied, it starts ballooning out to about 2 inches in diameter.

Your latest device looks like it would release before the tube was fully deflated. Maybe you could get longer delays with smaller tubes if the tube needed to fully deflate.

My idea was to use a small pill bottle with a hole slightly larger than the hose's diameter drilled in its bottom. This design would also use a long 1/4 inch tube within the latex hose to inflate it. A disk the inside diameter of the pill bottle would be over the upper end of the hose just below the clamp to prevent the inflated hose from spilling out of the pill bottle. The hose would inflate inside the pill bottle. When it fully deflated, a spring would push the pill bottle upward over the hose.

Since I have cap-to-bottom Robinson coupled bottles, I plan to build the device within the top of a bottle. That way it can be screwed on as a module and get pressurized through the bottle cap below it.

I'm thinking of using removable threaded inserts made from small nylon bolts, with varying sizes of holes drilled through them, within the bottom end of the air tube to regulate deflation speeds. That should make it easy to change speeds out in the field.

Dennis

[Frank]

Sounds doable. Like most things, once the general principle is envisioned, there are initial builds, then variations on the theme, then multiple modifications which leads to a final, workable design that meets all the needs. If you quit early, usually you have no results to show for all your hard work. Keep exploring new materials and methods, and I'm sure you can succeed with your staging device.

I've no doubt that I could turn this parachute deployment method into a viable staging device, but I would certainly like to get some actual flight time in with single stages before adding THAT complexity to my rocket building. Right now, I'm sticking with the KISS principle (Keep It Simple, Stupid!).

I'm SERIOUSLY considering a "premature" launch of my rocket with a streamer instead of a parachute. Yesterday was super windy here, but this morning it is clear and calm. It will take me quite a while to build a proper parachute, but I could slap together a long streamer pretty easily. Since I've built removable fins, I could probably get away with no damage at all...just itching to flight test!!!!

We'll see!

Best to all,

Frank

[Spaceman Spiff]

Hi Frank,

Congratulations on your success with the device!

Last summer I bought some latex rubber hose to try to make a "crushing sleeve" type of staging device but never got very far into that idea. It is 1/4 inch i.d., 3/8 o.d., and was sold by the foot at Lowe's and I think it is available in long lengths at Home Depot. After seeing your idea here, I started thinking about using latex hose in your type of device.

When very low pressure is applied, it starts ballooning out to about 2 inches in diameter.

Your latest device looks like it would release before the tube was fully deflated. Maybe you could get longer delays with smaller tubes if the tube needed to fully deflate.

My idea was to use a small pill bottle with a hole slightly larger than the hose's diameter drilled in its bottom. This design would also use a long 1/4 inch tube within the latex hose to inflate it. A disk the inside diameter of the pill bottle would be over the upper end of the hose just below the clamp to prevent the inflated hose from spilling out of the pill bottle. The hose would inflate inside the pill bottle. When it fully deflated, a spring would push the pill bottle upward over the hose.

Since I have cap-to-bottom Robinson coupled bottles, I plan to build the device within the top of a bottle. That way it can be screwed on as a module and get pressurized through the bottle cap below it.

I'm thinking of using removable threaded inserts made from small nylon bolts, with varying sizes of holes drilled through them, within the bottom end of the air tube to regulate deflation speeds. That should make it easy to change speeds out in the field.

Dennis

The guys at AntiGravityResearch had a launcher that used a latex nipple to do the same thing you want to do with the latex hose. They took advantage of the fact that the nipple "herniated" (Thanks for the term I needed to describe the action!) and used that to hold the launcher on their pad. A tiny hole would allow the air to get into the bottle and also prevented the nipple from simply bursting. As long as you kept pumping, the nipple would have a pressure difference and would hold the rocket on the pad.

[Frank]

Hey, guys & gals:

The miniaturization of this bladder controlled parachute deployment system is really progressing nicely. Here's my latest, lightest, most reliable version yet! This puppy is ready to FLY!!! Every test has proven its reliability and has been tested to 100 PSI. Simple and cheap to construct, no electronic components, just a couple of pieces of cheap PVC, couple of inches of bicycle tire inner tube and a cut up rubber band will propel your nose cone off with authority at the end of the thrust phase, every time! Weighs only a handful of grams and with some outlet obstruction, can delay deployment of the parachute. The delay can be dialed in on the bench, without need to fly it.

Here it is in the inflated state (VERY low pressure) without the PVC bearing tube to illustrate the way in which the tire balloons out to secure the bearing tube built into the nose cone. I hope several folk will build this and employ it to deploy their chutes. If you do, kindly provide your feedback and/or videos to this thread.

Best regards to all,

Frank S.